In the third generation mobile communications method represented by IMT-2000 (International Mobile Telecommunications-2000), a high speed and large capacity downlink is required. For example, an information transmission rate of 2 Mbps has been realized using a frequency bandwidth of 5 MHz. In one of the IMT-2000 systems, single carrier W-CDMA (Wideband-CDMA) has been employed. In addition, a method called High Speed Downlink Packet Access (HSDPA) may be used. The HSDPA enables a high transmission rate and a high quality transmission by employing an Adaptive Modulation and channel Coding (AMC) method, an Automatic Repeat Request (ARQ) method in an MAC layer, or the like. The AMC is described, for example, in Non-patent Publication 1. The ARQ is described, for example, in Non-patent Publication 2. A technology in which a frequency band is divided into plural bands (frequency blocks) and a modulation method is determined for every frequency block is described in Non-patent Publication 3.    Non-patent Publication 1: T. Ue, S. Aampei, N. Morinaga and K. Hamaguchi, “Symbol Rate and Modulation Levelel-Controlled Adaptive Modulation/TDMA/TDD System for High-Bit-Rate Wireless Data Transmission”, IEEE Trans. VT, pp. 1134-1147, vol. 47, No. 4, November 1998.    Non-patent Publication 2: S. Lin, Costello, Jr. and M. Miller, “Automatic-Repeat-Request Error Control Schemes”, IEEE Communication Magazine, vol. 12, No. 12, pp. 5-17, December 1984.    Non-patent Publication 3: P. Chow, J. Cioffi, J. Bingham, “A Practical Discrete Multitone Transceiver Loading Algorithm for Data Transmission over Spectrally Shaped Channel”, IEEE Trans. Commun. vol. 43, No. 2/3/4, February/March/April 1995.